package settings

import (
	"dns_service/utils"
	"fmt"
	"os"
	"strings"
)

// Helper to write file content
func writeFile(path, content string) error {
	return os.WriteFile(path, []byte(content), 0644)
}

func SetSettings(new_settings map[string]any) (map[string]any, error) {
	// 1. Get config path and read the main dnsmasq configuration
	configPath := os.Getenv("DNSMASQ_CONFIG")
	if configPath == "" {
		return nil, fmt.Errorf("DNSMASQ_CONFIG environment variable not set")
	}

	data, err := os.ReadFile(configPath)
	if err != nil {
		return nil, fmt.Errorf("failed to read config file at %s: %w", configPath, err)
	}
	dnsmasqSettings := utils.DecodeSettings(string(data), "\n", "=")

	// 2. Update cache-size in the main config file
	if newCacheSize, ok := new_settings["cache_size"]; ok {
		oldCacheSize, oldOk := dnsmasqSettings["cache-size"]
		// Replace the line if it exists, otherwise dnsmasq uses a default
		if oldOk {
			newConfigContent := strings.Replace(
				string(data),
				"cache-size="+oldCacheSize,
				"cache-size="+fmt.Sprintf("%v", newCacheSize),
				1,
			)
			if err := writeFile(configPath, newConfigContent); err != nil {
				return nil, fmt.Errorf("failed to write updated config to %s: %w", configPath, err)
			}
		}
	}

	// 3. Update the resolv file
	if newResolvs, ok := new_settings["resolv"].([]any); ok {
		resolvFile, ok := dnsmasqSettings["resolv-file"]
		if !ok {
			return nil, fmt.Errorf("resolv-file path not found in dnsmasq config")
		}
		var b strings.Builder
		for _, v := range newResolvs {
			if s, ok := v.(string); ok {
				fmt.Fprintf(&b, "nameserver %s\n", s)
			}
		}
		if err := writeFile(resolvFile, b.String()); err != nil {
			return nil, fmt.Errorf("failed to write to resolv file %s: %w", resolvFile, err)
		}
	}

	// 4. Update the hosts file
	if newHosts, ok := new_settings["hosts"].(map[string]any); ok {
		hostsFile, ok := dnsmasqSettings["addn-hosts"]
		if !ok {
			return nil, fmt.Errorf("addn-hosts path not found in dnsmasq config")
		}
		var b strings.Builder
		for key, value := range newHosts {
			b.WriteString(key)
			switch v := value.(type) {
			case []any:
				for _, ip := range v {
					fmt.Fprintf(&b, " %s", ip)
				}
				b.WriteString("\n")
			case string:
				fmt.Fprintf(&b, " %s\n", v)
			}
		}
		if err := writeFile(hostsFile, b.String()); err != nil {
			return nil, fmt.Errorf("failed to write to hosts file %s: %w", hostsFile, err)
		}
	}

	// 5. Restart dnsmasq to apply changes
	if err := utils.RestartDnsmasq(); err != nil {
		return nil, fmt.Errorf("failed to restart dnsmasq: %w", err)
	}

	return new_settings, nil
}